1989 merc burnt piston..... fuel pump,oil pump

[reynold460]

hi guys i have a 1989 115 hp 2+2 motor serial number oc106992 that burnt the # 2 piston up last year i have been slowly rebuilding it this winter heres what happened and what i have found since taking on this project.
at this point i have the motor pretty much back together , i have been trying to find out what had caused the piston to burn up and have been unable to find anything as the carbs are spotless until i went to rebuild the fuel pump [ i have the 90 degree check valve pump] and i cannot blow thru the check valve in either direction it is blocked right off , so my pump is supposed to have a solid diaphragm and one with two holes in it [ i figure for the oil to get to the gas] anyhow when i take it apart i have two solid diaphragms , so i cant see how this motor was gettin any oil ?
i also took the covers off the oil pump and found very small metal fragments similar to glitter only smaller in size.
i want to bypass the oil pump and mix my gas.
and im worried the oil pump will lock up and harm the motor, so im thinking of taking the gear and shaft from the oiler off the motor so that the pump doesnt even turn, however i will put the pump etc on to seal the motor does any one see any problems with this and has anyone tried this .
what do you guys think about this ? thanks for any help

 

[Bosunsmate]

Re: 1989 merc burnt piston..... fuel pump,oil pump

I havent tried it on that motor but i recommend and do it on all motors i work on apart from if the owner really doesnt want to premix.
Clean your plugs, pull your lanyard line so it wont spark and crank it over a few times then check your plugs that they are all a similar wetness

 

[gbrowne9]

Re: 1989 merc burnt piston..... fuel pump,oil pump

i have the same motor that had the same piston problem.i rebuilt the motor and disconnected the oil injection because i didn,t trust it.that was 4 years ago and the motor is fine.i can,t believe how little fuel these motors use compared to the tower of power.you will need to mix 50:1 in the gas and lean out the mixture a bit.

 

[reynold460]

Re: 1989 merc burnt piston..... fuel pump,oil pump

thanks for the info. yea i had a 1984 t.o.p it was hard on gas , dont know about this motor this happend the second time i took it out after buying it sure hope it is tho

 

[reynold460]

Re: 1989 merc burnt piston..... fuel pump,oil pump

ok so i put the powerhead back on the lower section and went to put the shift cable back on , i went to slide the shift mechanism to neutral and it wont lock into neutral , i can hold the slider there and its in neutral but it wont stay in neutral on its own .
the shift shaft was turned way out of its normal travel when i went to put it back on , could this be a shift cam problem or the shift cam turned too far and the balls in the cam follower fell out , this lower unit worked flawlessly before i removed the powerhead thanks for any help you can give,

 

[Bosunsmate]

Re: 1989 merc burnt piston..... fuel pump,oil pump

Does it go in f R ok?
you may have rotated cam by 180 degrees so itl need turning 180degrees again to get it back on the siide with the neutral indentation again. Careful which way you spin it to correct it as one way uses a lot more pressure than the other

 

[reynold460]

Re: 1989 merc burnt piston..... fuel pump,oil pump

yea it seems to go into foward and reverse ok